Conventionally, an imaging device having an optical system shown in FIG. 11 is known as a monocular stereoscopic imaging device (Patent Literature 1).
This optical system has a configuration in which object images having passed through different regions in the horizontal direction of a main lens 1 and a relay lens 2 are pupil-divided by a mirror 4 and are imaged onto imaging elements 7 and 8 through image-forming lenses 5 and 6, respectively.
FIGS. 12(A) to 12(C) show separate states of an image that is imaged onto an imaging element depending on difference among front-focus, in-focus (best focus), and back-focus. In FIG. 12, in order to compare the difference in the separate state by the focusing, the mirror 4 shown in FIG. 11 is omitted.
Among the pupil-divided images, images that are in focus are imaged (matched) at the same position on the imaging element as shown in FIG. 12(B), whereas images that are front and back focused are imaged (separated) at different positions on the imaging element as shown in FIGS. 12(A) and 12(C).
Accordingly, by obtaining object images pupil-divided in the horizontal direction via the imaging elements 7 and 8, a left viewpoint image and a right viewpoint image (3D image), in which viewpoints are different depending on an object distance, can be obtained.
Patent Literature 2 discloses an example of compound-eye stereoscopic imaging device. This imaging device measures a camera shake from a photographed 3D image. When the correction amount of camera shake exceeds a predetermined value, the imaging device determines that the 3D image is not suitable for a stereoscopic view and causes a 2D data creation unit to output photographed image data.
Patent Literature 3 discloses an example of a camera-shake correction mechanism of a compound-eye stereoscopic imaging device.
Patent literature 4 discloses an example of a camera-shake correction mechanism of a monocular camera equipped with a stereo adapter.
Patent Literature 5 discloses an example of a camera provided with an optical camera-shake correction mechanism. The amount of camera shake in a yaw direction ωx and the amount of camera shake in a pitch direction ωy can be obtained by calculating a displacement angle ωx and angular velocity ωx around the y-axis and a displacement angle ωy and angular velocity coy around the x-axis from acceleration a1x and a2x in the x-axis direction and acceleration a1y and a2y in the y-axis direction, respectively.
It is known that when a body to be an object is imaged onto an imaging surface of an imaging element by using an optical system such as a zooming lens, blurring occurs in an image imaged by the imaging element compared to the original body due to an influence of aberration of the optical system, and the image quality is reduced. The intensity distribution of g of the then image is represented byg=f*h+n(* expresses convolution integral)  (A)where noise n is added to the convolution of the luminance distribution f of the original body and the point spread function h that is indicative of the image-forming capability of the optical system. The elements g, h, and n being already known, the luminance distribution f of the original body can be calculated by the formula (A). The technique that removes blurring of an optical system by signal processing and obtains an ideal image like this is called “restoration”, “reverse convolution”, or “deconvolution” of the image. A restoration filter based on the point spread function (PSF) is generated in consideration of information of degradation of an image at the time of imaging such as an imaging condition (for example, exposure time, light exposure, a distance to an object, a focusing length) and characteristic information of an imaging device (for example, optical characteristics of a lens, identification information of an imaging device) (Patent Literature 6).
A degradation model based on blurring can be expressed as a function. For example, a blurring phenomenon can be expressed by a normal distribution using a distance (image height) from the center pixel as a parameter (Patent Literature 7).
Patent literature 8 discloses an example of aperture control of an imaging device. A camera is controlled to increase light quantity to a solid-state imaging element by using an extra maximum aperture at the time of photographing by electronic zooming. As a result, a shutter speed can be speeded up, and a camera shake can be prevented. Besides, the camera shake easily occurs as a focusing length of a photographic optical system is closer to the TELE side, however, little camera shake may be indistinctive when photographing is performed at a low resolution. Accordingly, the amount of blurring (the amount of shake) of an image due to the camera shake is calculated, the calculated amount of blurring and image performance data at the extra maximum aperture are compared, and then, in the case where the amount of blurring due to the camera shake exceeds the influence of degradation of the image performance, the photographing is performed in the balance point of the camera shake and the image performance by speeding up a shutter speed using the extra maximum aperture.